U.S. Pat. No. 4,252,210 discloses methods of and apparatus for generating seismic waves and discloses background information concerning the production of seismic waves including publications and patents.
The apparatus disclosed in U.S. Pat. No. 4,252,210 includes a tubular expandable outer wall closed at each end by rigid, high-strength closure members to which two different pressures applied from an external hydraulic reservoir, one for anchoring the generator to the wall and the second of greater intensity to provide the radiated waves which are directed only to the walls of the well bore. This apparatus has the advantages mentioned in said patent but is limited as to depths in use because of the external hydraulic reservoir and the hydraulic lines to and from the apparatus.
Other background disclosures include the following patents: U.S. Pat. No. 4,751,688 dated June 14, 1988 "Downhole Electromagnetic Seismic Source," U.S. Pat. No. 4,715,470 dated Dec. 29, 1987 "Downhole Electromagnetic Seismic Source," and U.S. Pat. No. 4,702,343 dated Oct. 27, 1987 "Nondestructive Downhole Seismic Vibrator to Obtain Information about Geologic Formations."
It would be highly desirable to provide an apparatus for generating seismic waves at greater depths than is practical for the apparatus disclosed in U.S. Pat. No. 4,252,210, for example, one which permits generation of seismic energy within a well bore to depths of 10,000 feet and more and in which the energy generated is of sufficient power and character as to produce suitable displacement on remotely located receivers or sensors (geophones) so as to be recorded and later recognized when processed by preprogrammed computers. It would also be advantageous to provide such an apparatus with self-contained hydraulic reservoirs and pumps and, accordingly, can be lowered into the well bore, anchored at a number of well bore locations, and removed from the well bore, all on conventional wire line equipment similar to that used for electrical logging and other operations in the well bore.